1. Field of the Invention
This invention pertains to the field of liquid dispensing equipment. More particularly, it pertains to a method of making a novel nozzle that is applicable to manufacture of nozzles with constant or varying wall thickness. The technique will produce metallic nozzles with very thin rigid walls from metals that have a tendency to become hard and rigid when worked into final shape.
2. Description of the Prior Art
Nozzles made for dispensing of viscous fluids are produced in a variety of different ways. The method and material selected are a function of the general category.
At present there are three general types of nozzles used to underfill electronic devices with viscous liquid: (1) a modified hypodermic needle made of stainless steel and medical tubing, (2) a custom machined metal nozzle, and (3) a molded plastic cone-shaped nozzle. The modified hypodermic needle nozzle is merely a standard hypodermic needle adapted to fit to a standard valve (Luer or Luer lock type) and attached to a hose leading from a pump that is connected to a reservoir of liquid. Modified hypodermic needles have a constant diameter throughout the length. This causes a very high-pressure drop across the needle and restricts liquid flow. In addition, the needle is made from stainless steel, plastic, or brass. Stainless steel and plastic are not known as good heat transfer materials. The fluid path is not contiguous and usually constrictive at the connection point. Transition points of the flow channel through the nozzle using this manufacturing technique are abrupt and inconsistent. The custom machined nozzle may be made of better heat transfer materials and may be shaped to remove or, at least, greatly reduce the resistance produced in the hypodermic needle design. However, a machined nozzle is limited to the size of the tools that can be used to cut the inside wall diameter and the wall thickness that must be maintained to ensure cuts are made without deformation of the nozzle. Machining of nozzles can be applied to one and two-piece designs, any shape can be made that can be programmed to cut using computer controlled lathes or form tools ground for the purpose. It is difficult to make very small gage sizes, almost impossible if the nozzle wall is thin. These limitations, along with the high cost of machining minute nozzles of this type, have slowed the widespread use of such nozzles in the industry.
The molded plastic nozzle is the lowest cost nozzle produced, it can be made in a variety of sizes and shapes out of a number of engineering polymers using plastic injection molding. However, plastics are not good agents of heat transfer, they are not dimensionally stable, require a relatively loose tolerance, expand and contract when exposed to high intermittent pressures and have threads that have little resistance to failure by over tightening. Such a practice has not been well accepted in the industry. The modified hypodermic needle remains the most widely used nozzle.
3. Objects and Advantages
Accordingly, the method of making the nozzle has inherent objects and advantages that were not described earlier in my patent. Several additional objects and advantages of the present invention are:                (1.) To provide a method of producing a nozzle wherein Process enables a constant thickness wall at the core inlet, selectively thinning the core wall between various sections to achieve a wall thin enough to allow a punch to pierce the section without fracture. Through experimentation it has been found the equationPcPf=12.0535−0.268653*Gage−1445.17*Wallwill yield suitable results for prediction of Carbide punch failure for a given section composed of copper alloy, apriori. Simplified empirical equation fit from data using Ridge Regression Techniques is accurate within a range of 0.001 in to 0.005 in. in wall thickness. Values of Pc/Pf; the Critical Punch Force/Force To Punch The Hole approaching Pc/Pf<=1, indicate punch fracture from the force required to pierce thru the nozzle wall.        (2.) To provide a method of producing a conically shaped exit aperture; radial clearance between punch and die can be adjusted to vary the conical depth through the exit aperture wall.        (3.) To provide a method of producing a nozzle wherein the thinness of the nozzle wall is such that geometry for features, rifling or striations or other like details can be built into the outside wall of the die cavity. Metal forced against the die side bends inward to produce a raised image of the geometry on the inside of the nozzle cavity.        (4.) To provide a method of producing a nozzle wherein soft, ductile, thermally efficient, conductive metals can be cold worked to the extent the metal effectively hardens and becomes rigid. Copper and copper alloys are the best candidates for the process.        (5.) To provide a method of producing a nozzle wherein Process is fast and low cost to proliferate the use of the technology in the industry.        (6.) To provide a method of producing a nozzle wherein very low Nozzle-to-Nozzle variability is a result of exceptionally tight tooling tolerances enabled by the process. Nozzle bore tolerance is routinely held to ten thousandths of an inch.        (7.) The high aspect ratio of the process produces a nozzle core that is composed of one piece or contiguous.        (8.) The Process can produce compound bend radii as tight as 0.0014 inch on a 0.0014-inch thick wall with copper alloys. The ratio wall thickness/bend radii can be as large as 1.0 using this material in the annealed or softened condition.Thinner walls also provide less facial area at the base upon which liquid can adhere resulting in a cleaner break-off of the dispensed liquid. The thinner wall also results in the smallest difference between the surface areas on the exterior, as opposed to the interior. This provides less surface tension forces, which direct the fluid to accumulate on the exterior of the nozzle. Thus more liquid is held on the interior of the nozzle improving both speed and accuracy of dispensing and of the automated dispensing equipment upon which it may be used. Additionally, the material making up the nozzle must have good heat transfer characteristics. This enables reduction of viscosity in most liquids, thereby enhancing the dispensability of the liquid. Further, the thinner wall also enables a more uniform and rapid thermal response to the entire nozzle body. Finally, thinner walls enable dispensing on densely populated circuitry, effectively depositing fluid closer to the chip.        